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galaxy clusters
Ram pressure stripping: a classic paper
A classic 1972 paper by Jim Gunn and J. Richard Gott, III describing the growth of clusters from primordial density perturbations and, most famously, the importance of ram pressure stripping in explaining the observed lack of spiral galaxies towards the center of clusters.
The Top 12 of 2012
What were astronomers reading and talking about in their research last year? Check out figures from the top 12 most-cited astronomy papers from 2012 (so far) and find out what researchers were up to and why!
Gravitational Lensing in the Canary Islands
I recently attended a two-week crash course in the “Astrophysical Applications of Gravitational Lensing”. In this post, I overview a few of the ways astronomers employ lensing to study the Universe, from extrasolar planets to distant quasars and large-scale structure.
Observing the Velocity Anisotropy of Cluster Galaxies
Title: Spatial Anisotropy of Galaxy Kinematics in Sloan Digital Sky Survey Galaxy Clusters First Author: Skielboe, A. Galaxy clusters are beautifully simple, but also fantastically complicated structures. For many years, astronomers have treated these systems as spherical cows, but simulations and observations have repeatedly shown that clusters exhibit triaxial rather than spherical shapes with nice [...]
Mixing up gas in the wake of a strangled satellite
Most simulations to date have implied that satellite galaxies traveling through galaxy clusters are stripped of gas for future star formation in a process known as “strangulation”. In contrast, the authors of this paper suggest that satellite galaxies may not be as cut off as some might think: instead, their simulations show that the cooler, stripped gas from the corona will mix with the surrounding intra-cluster medium and remain near the original galaxy as a potential new source of star-forming fuel.
Strands in the Cosmic Web
Throughout much of the 20th century, it was an open question in astronomy as to what the universe looked like on the largest observable scales. Were galaxies and galaxy clusters distributed uniformly throughout space, or was there a pattern? Thanks to galaxy surveys we know that, on large scales, the matter distribution of the universe is clumpy instead of smooth. Through these surveys we observe directly the distribution of luminous matter like stars, gas, and galaxies. However, luminous matter comprises only a small fraction of the matter in the universe (17%), the rest is dark matter which interacts via gravity but does not absorb and emit electromagnetic radiation like normal matter. Theoretical simulations of dark matter cosmologies firmly predict that there is a dark matter backbone to the cosmic web, with filaments of dark matter stretching between clusters of galaxies, though has not yet been a robust detection of a dark matter filament, until now.
The Lensing Galaxy Cluster That Shouldn’t Exist
The authors discover a strong lensing arc behind an unusually massive galaxy cluster at high redshift. The existence of such a lensing system at high redshift is found to be inconsistent with the standard cosmological model.
The biggest black holes may be bigger than we thought
A team of astronomers at the University of Cambridge have uncovered evidence for ultramassive black holes in the giant elliptical galaxies that sit at the center of galaxy clusters. These whoppers could be up to ten times more massive than ordinary supermassive black holes, like the ones we usually find in centers of galaxies.
NGC 6864 vs. NGC 6229: Dueling Blue Straggler Populations
Blue stragglers are stars within a globular cluster that lie along an extension of the main-sequence, above the turnoff point. As such they appear to be much younger than the rest of their stellar population. Current research suggests that they form by coalescence of mass-transfer between two companions in a binary system and the merger of two stars induced by stellar collision. By observing the population distributions of blue stragglers in globular clusters we can learn about the mechanisms through which they formed and the evolutionary dynamics of the cluster itself.
Stellar Archeology: A Cosmological View of Dwarf Galaxies
Living metal-poor stars represent the fossil records of the early cosmic star formation.
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